/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE
 * file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file
 * to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */
package com.blade.web.multipart;

import java.util.HashMap;
import java.util.Map;

/**
 * A simple parser intended to parse sequences of name/value pairs. Parameter values are expected to be enclosed in
 * quotes if they contain unsafe characters, such as '=' characters or separators. Parameter values are optional and can
 * be omitted.
 *
 * <p>
 * <code>param1 = value; param2 = "anything goes; really"; param3</code>
 * </p>
 *
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 */
public class ParameterParser {
	/**
	 * String to be parsed.
	 */
	private char[] chars = null;

	/**
	 * Current position in the string.
	 */
	private int pos = 0;

	/**
	 * Maximum position in the string.
	 */
	private int len = 0;

	/**
	 * Start of a token.
	 */
	private int i1 = 0;

	/**
	 * End of a token.
	 */
	private int i2 = 0;

	/**
	 * Whether names stored in the map should be converted to lower case.
	 */
	private boolean lowerCaseNames = false;

	/**
	 * Default ParameterParser constructor.
	 */
	public ParameterParser() {
		super();
	}

	/**
	 * Are there any characters left to parse?
	 *
	 * @return <tt>true</tt> if there are unparsed characters, <tt>false</tt> otherwise.
	 */
	private boolean hasChar() {
		return this.pos < this.len;
	}

	/**
	 * A helper method to process the parsed token. This method removes leading and trailing blanks as well as enclosing
	 * quotation marks, when necessary.
	 *
	 * @param quoted <tt>true</tt> if quotation marks are expected, <tt>false</tt> otherwise.
	 * @return the token
	 */
	private String getToken(boolean quoted) {
		// Trim leading white spaces
		while ((i1 < i2) && (Character.isWhitespace(chars[i1]))) {
			i1++;
		}
		// Trim trailing white spaces
		while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1]))) {
			i2--;
		}
		// Strip away quotation marks if necessary
		if (quoted) {
			if (((i2 - i1) >= 2) && (chars[i1] == '"') && (chars[i2 - 1] == '"')) {
				i1++;
				i2--;
			}
		}
		String result = null;
		if (i2 > i1) {
			result = new String(chars, i1, i2 - i1);
		}
		return result;
	}

	/**
	 * Tests if the given character is present in the array of characters.
	 *
	 * @param ch the character to test for presense in the array of characters
	 * @param charray the array of characters to test against
	 *
	 * @return <tt>true</tt> if the character is present in the array of characters, <tt>false</tt> otherwise.
	 */
	private boolean isOneOf(char ch, final char[] charray) {
		boolean result = false;
		for (int i = 0; i < charray.length; i++) {
			if (ch == charray[i]) {
				result = true;
				break;
			}
		}
		return result;
	}

	/**
	 * Parses out a token until any of the given terminators is encountered.
	 *
	 * @param terminators the array of terminating characters. Any of these characters when encountered signify the end
	 *            of the token
	 *
	 * @return the token
	 */
	private String parseToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		while (hasChar()) {
			ch = chars[pos];
			if (isOneOf(ch, terminators)) {
				break;
			}
			i2++;
			pos++;
		}
		return getToken(false);
	}

	/**
	 * Parses out a token until any of the given terminators is encountered outside the quotation marks.
	 *
	 * @param terminators the array of terminating characters. Any of these characters when encountered outside the
	 *            quotation marks signify the end of the token
	 *
	 * @return the token
	 */
	private String parseQuotedToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		boolean quoted = false;
		boolean charEscaped = false;
		while (hasChar()) {
			ch = chars[pos];
			if (!quoted && isOneOf(ch, terminators)) {
				break;
			}
			if (!charEscaped && ch == '"') {
				quoted = !quoted;
			}
			charEscaped = (!charEscaped && ch == '\\');
			i2++;
			pos++;

		}
		return getToken(true);
	}

	/**
	 * Returns <tt>true</tt> if parameter names are to be converted to lower case when name/value pairs are parsed.
	 *
	 * @return <tt>true</tt> if parameter names are to be converted to lower case when name/value pairs are parsed.
	 *         Otherwise returns <tt>false</tt>
	 */
	public boolean isLowerCaseNames() {
		return this.lowerCaseNames;
	}

	/**
	 * Sets the flag if parameter names are to be converted to lower case when name/value pairs are parsed.
	 *
	 * @param b <tt>true</tt> if parameter names are to be converted to lower case when name/value pairs are parsed.
	 *            <tt>false</tt> otherwise.
	 */
	public void setLowerCaseNames(boolean b) {
		this.lowerCaseNames = b;
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are expected to be unique. Multiple separators
	 * may be specified and the earliest found in the input string is used.
	 *
	 * @param str the string that contains a sequence of name/value pairs
	 * @param separators the name/value pairs separators
	 *
	 * @return a map of name/value pairs
	 */
	public Map<String,String> parse(final String str, char[] separators) {
		if (separators == null || separators.length == 0) {
			return new HashMap<String,String>();
		}
		char separator = separators[0];
		if (str != null) {
			int idx = str.length();
			for (int i = 0; i < separators.length; i++) {
				int tmp = str.indexOf(separators[i]);
				if (tmp != -1) {
					if (tmp < idx) {
						idx = tmp;
						separator = separators[i];
					}
				}
			}
		}
		return parse(str, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are expected to be unique.
	 *
	 * @param str the string that contains a sequence of name/value pairs
	 * @param separator the name/value pairs separator
	 *
	 * @return a map of name/value pairs
	 */
	public Map<String,String> parse(final String str, char separator) {
		if (str == null) {
			return new HashMap<String,String>();
		}
		return parse(str.toCharArray(), separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of characters. Names are expected to be unique.
	 *
	 * @param chars the array of characters that contains a sequence of name/value pairs
	 * @param separator the name/value pairs separator
	 *
	 * @return a map of name/value pairs
	 */
	public Map<String,String> parse(final char[] chars, char separator) {
		if (chars == null) {
			return new HashMap<String,String>();
		}
		return parse(chars, 0, chars.length, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of characters. Names are expected to be unique.
	 *
	 * @param chars the array of characters that contains a sequence of name/value pairs
	 * @param offset - the initial offset.
	 * @param length - the length.
	 * @param separator the name/value pairs separator
	 *
	 * @return a map of name/value pairs
	 */
	public Map<String,String> parse(final char[] chars, int offset, int length, char separator) {

		if (chars == null) {
			return new HashMap<String,String>();
		}
		HashMap<String,String> params = new HashMap<String,String>();
		this.chars = chars;
		this.pos = offset;
		this.len = length;

		String paramName = null;
		String paramValue = null;
		while (hasChar()) {
			paramName = parseToken(new char[] { '=', separator });
			paramValue = null;
			if (hasChar() && (chars[pos] == '=')) {
				pos++; // skip '='
				paramValue = parseQuotedToken(new char[] { separator });
			}
			if (hasChar() && (chars[pos] == separator)) {
				pos++; // skip separator
			}
			if ((paramName != null) && (paramName.length() > 0)) {
				if (this.lowerCaseNames) {
					paramName = paramName.toLowerCase();
				}
				params.put(paramName, paramValue);
			}
		}
		return params;
	}
}
